The present invention relates to improvement of a scanning tunneling microscope and in particular to a tunneling acoustic microscope so improved as to be suitable for observing lattice strain caused within a sample.
Conventional scanning tunneling microscopes (hereafter abbreviated to STMs) are discussed in U.S. Pat. Nos. 4,618,767, 4,668,865, and Appl. Phys. Lett. 40(2), 1982, pp. 178-180.
The configuration based upon the principle of an STM will now be described. That is to say, a tungsten tip is so disposed as to be close to the surface of a conductive sample, and a tunneling current is let flow between them. The tip or the sample is scanned while the gap between the tip and the sample is so adjusted that the tunneling current may be kept constant. Topographies on the surface of the sample are thus obtained.
In the above described prior art, derivation of topographies such as corrugation on the surface of the sample is mainly described. Derivation of information concerning the inside of the sample and concrete means for that purpose are not presented. Further, the case where the sample is an insulator is not considered.